Shell of a sports shoe, in particular a ski boot, and a method of producing such a shell

ABSTRACT

The invention relates to a shell of a sports shoe, in particular a ski boot, comprising at least one shell part having at least one stiffening part, which has a higher stability than the other components of the shell parts. One or more spacers protrude from an interior surface of the stiffening part. A portion of the shell is formed from a relatively flexible plastic material compared to the stiffening part. Furthermore, a method for producing an above-mentioned shell of a sports shoe is described.

The invention relates to a shell of a sports shoe, in particular a skiboot, and a method for producing the shell of a sports shoe, inparticular a ski boot, as it is described in the claims 1 to 14.

From prior art it is known to build such a shell from one or severalshell parts being connected in an articulated way and comprising severalcomponents, with the components of the shell parts being preferablyformed from different materials in order to particularly achieve shellparts providing high stability or dimensional stability.

Document GB 1 491 634 shows a shell of a sports shoe produced by aninjection molding process and a method of making the shell. In order toincrease the extension stiffness and fixedness of the elastic injectionmolding material of the shell, a porous, fabric-like insert isadditionally integrated into the shell and the injection moldingmaterial shall penetrate and surround the insert during the productionprocess. The porous insert is made of several layers of synthetic fabricor plastic foil and is placed exactly in the region of the sports shoe,where the highest stiffness and fixedness is required or provided.According to the shown method, at first the porous, fabric-like insertis mounted to the foot-shaped last, then the outer injection moldingtool is positioned above the last and the insert thereon and finally,the injection molding material, such for example polyurethane, isinserted into the space between the last and the injection molding tool.In this case, the injection molding material should not only penetratethe porous insert, bur also lift it slightly from the last with theresult that the insert is surrounded by the injection molding materialcompletely and a homogenous shell part is formed. Particularly theslight lifting of the insert from the foot-shaped last represents aprocedural step which is hard to control, with the result that it cannotbe always ensured that the insert is surrounded by the injectionmaterial completely. Due to the desired complete overmolding of theinsert, it is furthermore possible to perform e.g. a simple positioncontrol of the insert for reasons of quality control, once the shell hasbeen produced successfully.

Document EP 0 808 708 A1 discloses an injection molding method inparticular for shell parts of a sports shoe, where at first an injectionmolding material being in its cured state relatively soft is insertedinto the injection mold so as to create channels in the producedinjection molded part. In a second procedural step, these channels, andalso the thereto adjacent regions of the injection molded part of therelatively soft material are injection-overmolded by an injectionmolding material being relatively rigid in its cured state in order toincrease the stability or the fixedness of the sports shoe. Due to theinjection-overmolding beyond the region of the channels, the injectionmolding material being relatively rigid in its cured state can beprevented from seeping at the upper edges of the channels during thesecond manufacturing step, because it is not required to position theinjection mold exactly at the upper edges of the channels in a sealingway, but it adjoins the injection molded part formed of relatively softinjection molding material face-to-face slightly beyond the channels.Thus, greater tolerances during positioning or dimensions of theinjection molding tool or the injection molded parts are allowed,resulting in less defective goods being produced. The specific fillingof the channels with the injection molding material being relativelyrigid in its cured state during a second injection molding process putsnevertheless increased technical requirements on the machine used forthe injection molding process.

The underlying objective of the present invention is to create a shellof a sports shoe, in particular a ski boot, which is pleasant andcomfortable to wear on the one hand, and the shell of which allows quickand sporty going or moving on the other hand. Additionally, theobjective of the present invention is to provide a method for producingsuch a shell of a sports shoe, in particular a ski boot, which can beperformed in an easy way and provides an increased practical suitabilityat the same time.

The firstly mentioned objective of the invention is achieved by a shellof a sports shoe according to the features in claim 1.

According to the invention, the shell of a sports shoe, in particular ofa ski boot, comprises one or more shell parts and furthermore, at leastone of these shell parts comprises three-dimensional components, whichare formed from a plastic material or metal having a defined stabilityor elasticity. At least one of these three-dimensional components of ashell part is formed as a stiffening part providing a higher stabilitythan the other components of the shell parts. By correspondingarrangement of the stiffening part, the stability or dimensionalstability in certain regions of the shell of a sports shoe is greatlyincreased. As a result, for example the stability of a front foot shellin the area of heel, ankle, sole and/or toes of a ski boot can beincreased correspondingly. This allows a faster, sportier going moreaccurately through the tracks, because a direct power transmission fromthe user's foot via the more stable ski boot and a binding to the ski isachieved.

By embodying of the section not covered by at least one stiffeningelement of a shell part formed from a relatively flexible plastics withrespect to the stiffening part, a sports shoe is created, which isconvenient and comfortable to wear due to the flexibility of the shellin the sections not being covered by stiffening parts. Due to the factthat the stability of the shell of the sports shoe is achieved in asufficient extent by the stiffening part(s) and the middle thickness ofthe shell can consequently be noticeably reduced compared to a shell nothaving stiffening parts, the weight of the shell of the sports shoe andconsequently the total weight of the sports shoe is furthermore reduced.Advantageously is furthermore a an alternative embodiment, which keepsthe middle thickness of the shell essentially the same compared to ashell without stiffening parts, with the stability of the plasticsrelatively flexible compared to the stiffening part being however chosenlower than usual, with the result that on the one hand, a shell havingsufficient stability is ensured by using the stiffening parts, and onthe other hand, a very flexible composition is present in the sectionsnot covered by stiffening elements, which also results in an increasedwearing comfort.

Furthermore, a very homogenous interior surface of the shell results,because also at least sections of the interior surface of the at leastone stiffening part are covered by the plastic material being relativelyflexible compared to the stiffening part. The homogeneity of theinterior surface is also not disturbed by the spacers being mounted tothe interior surface of the stiffening part, because the end sections ofthe spacers, which are farthest from the interior surface of thestiffening part, extend flush with the interior surface of the plastics,which is arranged on the interior surface of the stiffening part andrelatively flexible compared to the stiffening part. The one or theseveral spacers protruding from the interior surface of the stiffeningpart allow in a very easy way for the stiffening part to be positionedcorrectly and reliably on a last during the injection molding processfor producing the corresponding shell part. It is nevertheless alsopossible for the bearing surfaces of one or several spacers to bepartially covered by the relatively flexible plastics.

Due to the shell according to the invention, a sports shoe is created,which is, on the one hand convenient and comfortable to wear, and on theother hand, allows a fast and sporty going. This is of particularadvantage for a sports shoe, which is in its front shoe shell and/or thecuff equipped with one or more stiffening parts.

Of advantage is also an embodiment according to claim 2, because thementioned composite material for the at least one stiffening part can beworked in an easy way, in particular using an injection molding process.By contrast to the very laborious manufacturing process, where a fabricessentially formed from parallel fibers, is surrounded by a plasticmaterial and thus a fiber-reinforced plastics is produced, it is in thepresent case possible for the at least one stiffening part to beproduced in one relatively easy injection molding process. In this case,a plurality of fibers being independent from each other, are added tothe plastic material in a randomized arrangement, which are or will besurrounded by the plastic material. In addition to the simpleworkability of the composite material for the at least one stiffeningpart using a well-engineered injection molding process, said materialhas a very high modulus of elasticity of up to 12 GPa, preferably amodulus of elasticity of between 0.9 GPa and 1.5 GPa. Thus, high-tensilestiffening parts can be produced using said composite material.

Also of advantage are measures according to claim 3, because due to theminimum length of the fibers added to the plastic material a compositematerial is formed, which has a very high stability or a very highmodulus of elasticity. Furthermore, by defining the maximum length ofthe fibers added to the plastic material it is achieved that thisaddition can easily be performed directly during the injection moldingprocess for the production of the at least one stiffening part.

Also of advantage are measures according to claim 4, because due to theusage of a plastic material being relatively flexible compared to thestiffening part in the section of a part of the shell not covered by atleast one stiffening part, a shell of a sports shoe is created, whichhas relatively flexible certain regions and the sports shoe isconsequently convenient and comfortable to wear.

With respect to the measures according to claim 5 it is of advantagethat very lightweight shell parts and consequently sports shoes having avery low total weight can be produced by using a very thin stiffeningpart, which nevertheless has a sufficient stability due to the usedmaterial.

Also of advantage are measures according to claim 6, because the totalweight of the sports shoe is reduced at constant stability of the shellof the sports shoe due to the production of a relatively thin shell partcompared to the shell parts known from prior art.

Practical tests with present, classically constructed shells of a skiboot comprising a front foot shell and cuff thereto connected in anarticulated way and an appropriate new shell having stiffening partswithin the front foot shell and the cuff have shown that in the concretecase of an essentially constant stability of the shell, the weight ofthe front foot shell could be reduced from 870 g to 795 g and the weightof the cuff could be reduced from 410 g to 370 g. Consequently, due tothe construction of the shell according to the invention, a reduction ofweight of at least approximately 10% compared to a classicalconstruction of shell without stiffening parts can be achieved.

Of advantage are also measures according to claims 7 and 8, because theusage of such connection elements in the edge section of the at leastone stiffening part results in a very stable connection betweenstiffening part and the relatively flexible plastics adjacent thereto.Thus, the probability that the stiffening part detaches from or breaksout of the shell part or the relatively flexible plastics under load isreduced.

Of advantage are furthermore measures according to claim 9, because theinjection molding process for producing the shell part containing thestiffening part that can be seen from outside can thus performed in aneased and more reliable way. The reason is that the exterior surface ofthe stiffening part at least partially bears against the injection moldduring the injection molding process, with the result that it is allowedfor the stiffening part to be fixed safely in the injection moldtogether with the spacers at the interior surface. In this connection ofspecial advantage is also the embodiment, at which essentially theentire exterior surface of the at least one stiffening part is wellvisible or well accessible from the outside of the shell part, becausein this case, the stiffening part needs only to be injection-overmoldedor back-molded only at one side, namely only at the interior side.Furthermore, a visible exterior surface of the stiffening part which canbe seen at the exterior surface of the shell part increases theresistance or robustness of the exterior surface in the region of thestiffening part against mechanical affects. Additionally, the visibleexterior surface gives the shell part and consequently the entire shella very special appearance, with the result that a unique andunmistakable sports shoe is created and laying basis for the economicsuccess.

Of advantage are furthermore the measures according to claim 10, becausea sports shoe, depending on the case of usage, particularly in at leastone of the mentioned areas needs an increased stability and thisincrease of stability can easily be achieved by the arrangement of oneor more stiffening elements in these areas.

Very advantageous is furthermore an embodiment according to claim 11,because in many cases of application it is required for the shell of asports shoe to have an increased stability in the lateral region fromthe area of the heel and the Achilles' tendon in the direction towardsthe toe area to the inner and outer area of the ankle, with the resultthat a most direct possible power transmission from the foot or lowerleg of the user of the sports shoe to the sports shoe is provided. Thisis particularly applicable for forward and backward movements as well aslateral movements of the user's lower leg. A sole, which is stable inthe region described, thus allows an exact guiding of the sports shoe ora piece of sports equipment connected thereto, for example a glidingboard or a roller device during a movement.

Of particular advantage is also an embodiment according to claim 12,because the described, one-piece stiffening part causes a dimensionalstiffened shell formation in the inner and outer ankle area and in thearea of the heel or the Achilles' tendon and similarly provides arelatively flexible formation of the shell in the inner and outer tarsusarea, because the relatively flexible plastics forming the shell partthere, is not covered by the stiffening part. Examinations show thatwhen the foot is moved, particularly if the lower leg is moved forwardor is tilted back with respect to the foot, a lateral expansion of thefoot in the area inner and outer tarsus is caused. For example withrespect to the wear comfort it is thus advantageous if the shell of thesports shoe provides a relatively high flexibility in the area of theinner and outer tarsus. In order to not cause a too strong reduction ofstability of the shell of the sports shoe due to recesses in the regionof the inner and outer tarsus, it is furthermore of advantage if theedge section of the one-piece stiffening part underneath the areas ofinner and outer tarsus extends diagonally downwards or diagonally in thedirection towards the middle sole region and towards the toe area.

Advantageous is also an embodiment according to claim 13, because thus,a cuff for a sports shoe can be produced, which has a very stable backregion and rear lateral region, and similarly, the remaining section ofthe cuff not being covered by the stiffening part is formed relativelyflexible. As a result, the wear comfort of the sports shoe is increasedwithout its characteristics with respect to stability or moving arenegatively affected or the characteristics with respect to stability andmoving are even improved.

The secondly mentioned objective of the invention is achieved by amethod according to claim 14.

With respect to the measures according to claim 14 it is of advantagesthat the shell of a sports shoe is produced, the components of the shellparts of which have different, certain stability or elasticity and thatconsequently these characteristics can be adjusted exactly to the needsof the user corresponding to the intended purpose of the sports shoe.Furthermore, the usage of the one or more spacers protruding from theinterior surface of a stiffening part is of advantage, because thus theat least one stiffening part can easily be positioned on a last in sucha way that the outer end sections or bearing surfaces of the spacers,furthest from the interior surface of the stiffening part, bear againstthe surface of the last resulting in a clearance between the interiorsurface of the stiffening part and the surface of the last beingcreated. The injection-back-molding of the at least one stiffening partwith the result that the clearance between the interior surface of thestiffening part and the surface of the last is filled with relativelyflexible plastic material is thus allowed in an easy and reliable way,because the spacers hold the stiffening part in position and e.g. abearing of the interior surface of the stiffening part against thesurface of the last is avoided. Such a bearing of the interior surfaceof the stiffening part against the surface of the last would have anegative effect on the injection-back-molding process, because it wouldparticularly not be possible to apply sufficient flexible plasticmaterial to the interior surface of the stiffening part.

It is furthermore of particular advantage that the end sections orbearing surfaces of the spacers bearing against surface of the last arenot covered by the relatively flexible plastics and can consequently beseen and accessed at the interior surface of the shell part. Thus, asimple and reliable possibility to control the production quality isallowed, because the visible and accessible end sections or bearingsurfaces of the spacers allow that the correct position of thestiffening part in or at the shell part of the sports shoe iscontrolled. It is in particular easy to check the correct position ofthe end sections or the bearing surfaces of the spacers and consequentlythe stiffening part and the end sections or bearing surfaces extendingflush with the homogenous or constant interior surface of the shell ofthe sports shoe, which is very important.

To provide a clearer understanding of the invention, it will beexplained in more detail below with references to examples illustratedin the appended drawings.

The drawings provide highly simplified, schematic illustrations asfollows.

FIG. 1 the front foot shell of a ski boot having a stiffening part inthe area of the heel and the ankle;

FIG. 2 an oblique view of a stiffening part for the area of the heel andankle as it used with the front foot shell according to FIG. 1;

FIG. 3 a lateral view of the stiffening part of FIG. 2 for the area ofthe heel and ankle;

FIG. 4 a longitudinal section of the ski boot comprising the two shellparts front foot shell and cuff being connected in an articulated way,with the front foot shell separately shown in FIG. 1 having a stiffeningpart in the area of the heel and ankle and a stiffening part in theregion of the sole and the cuff having a stiffening part in the backregion and in the rear lateral regions;

FIG. 5 a cross-sectional view in the ankle area of the front foot shellof the ski boot of FIG. 4;

FIG. 6 an oblique view of the cuff of FIG. 4 having a stiffening part inthe back region and in the rear lateral regions.

Firstly, it should be pointed out that the same parts described in thedifferent embodiments are denoted by the same reference numbers and thesame component names and the disclosures made throughout the descriptioncan be transposed in terms of meaning to same parts bearing the samereference numbers or same component names. Furthermore, the positionschosen for the purposes of the description, such as top, bottom, side,etc. relate to the drawing specifically being described and can betransposed in terms of meaning to a new position when another positionis being described.

All value range specifications in the objective description should betaken as arbitrary ranges which encompass all subareas lying withinthese ranges, e.g. the specification 1 to 10 should be understood toencompass the full range starting from the bottom limit 1 and rising tothe top limit 10, i.e. all subareas start with a bottom limit of 1 ormore and end with a top limit of 10 or less, e.g. 1 to 1.7, or 3.2 to8.1, or 5.5 to 10.

As an exemplary embodiment of a shell 1 of a sports shoe, FIG. 1 shows afront foot shell 2 of a ski boot with a stiffening part 3 beingintegrated into the front foot shell 2. A ski boot of this kindtypically comprises, as known per se, an inner shoe inserted into theshell 1, at least one tensioning or lashing mean or other components,which have not been shown for increase of clarity.

The FIGS. 2 and 3 show an oblique view and a lateral view of thestiffening part 3 of the front foot shell 2.

According to the shown exemplary embodiment, the stiffening part 3 isdisposed in the heel area 10, area of Achilles's tendon 11 and in theinner 12 and outer ankle area 13 of a front foot shell 2 of a ski boot.The section 6 of the front foot shell 2 not being covered by thestiffening part 3 is formed from a plastic material which is relativelyflexible compared to the stiffening part 3. During the manufacturing ofthe front foot shell 2, in particular by means of an injection moldingprocess, the stiffening part 3 is injection-back-molded with therelatively flexible plastic material, with the result that the interiorsurface 4 of the stiffening part 3 is at least in partially butpreferably in large part covered by the relatively flexible plasticmaterial.

In the shown exemplary embodiment, the exterior surface 14 of thestiffening part 3 is not covered by the relatively flexible plasticmaterial. This is particularly functional, because amongst other thingsthe injection molding process for producing the front foot shell 2,containing the stiffening part 3 is made easier and more reliable interms of being successfully performed, because it is only required forthe stiffening part 3 to be injection-back-molded orinjection-overmolded on one side, namely the interior surface 4. Duringthe injection molding process, the exterior surface 14 at leastpartially bears against the injection mold, with the result that a safefixation of the stiffening part 3 within the injection mold is provided.An exterior surface 14 visible at the outside of the front foot shell 2furthermore increases the resistance or the robustness of the exteriorsurface in the region of the stiffening part 3 with respect tomechanical affects. Furthermore, the visible exterior surface 14 gives avery specific appearance to the front foot shell 2 and consequently tothe entire shell, with the result that a unique and distinctive ski bootis created. As it can be taken from FIG. 4, it is generally alsopossible for the exterior surface 46 of a stiffening part 3 to becovered by a relatively flexible plastic material.

In order to allow the already pre-manufactured stiffening part 3 to beeasily, exactly and safely positioned on a last, which at leastpartially defines the interior of the front foot shell 2, the stiffeningpart 3 is equipped with several spacers 5 protruding from its interiorsurface 4, the end sections 7 or bearing surfaces 8 of which restagainst the surface of the not shown last in the course of themanufacturing process. Thus, a clearance between the interior surface 4of the stiffening part and the surface of the last is formed, which isfilled with relatively flexible plastic material during the injectionmolding process. Once the injection molding process is completed, theentire surface 4 or the major part of the interior surface 4 of thestiffening part and the surface of the spacers 5, except from theirbearing surfaces 8, are consequently covered by the relatively flexibleplastic material. Due to the fact that these bearing surfaces 8 extendflush with the interior surface 9 of the plastic material disposed atthe interior surface 4 of the stiffening part 3, the front foot shell 2has a homogenous and constantly extending interior surface 9. In analternative embodiment, the sections of the bearing surface 8 of thespacers 5 can be covered by the relatively flexible plastic materiali.e. partially embedded into the relatively flexible plastic material.

With the exemplary embodiment shown, showing the front foot shell 2 of aski boot, preferably at least one one-piece stiffening part 3 ispositioned in the heel area 10, area of Achilles' tendon 11, and in theinner 12 and outer ankle area 13, with the result that particularly agood transmission of power and an exact transmission of motion of theuser's foot or the lower leg of ski boot via the rear extension of sole15 of the front foot shell 2 and via a binding in particular to a ski ispresent. Furthermore, the stiffening part 3 provides rear section of thefront foot shell 2 with sufficient stability. Additionally, thestiffening part 3 is formed in such a way, that the apertures 17 in theinner 12 and outer ankle area 13 of the front foot shell 2, serving forthe articulated connection of the front foot shell 2 and a cuff 18—FIG.4—of the ski boot, are embodied within the area of the front foot shell2 covered by the stiffening part 3, with the result that the apertures17, as it is best to be seen in FIGS. 2 and 3, are also embodied in thestiffening part 3 in the inner 12 and outer ankle area 13.

According to the particularly advantageous embodiment in FIG. 1, theone-piece stiffening part 3 of the front foot shell 2 covers the lateralareas of the front foot shell 2 starting from the heel area 10 and thearea of Achilles' tendon to the inner 12 and outer ankle area 13. It isfunctional if the stiffening part 3 also covers the inner 19 and outerareas of ankle joint 20 of the front foot shell 2, with the result thatan increased stability is given in these areas. In order to achieve thatthe front foot shell 2 at least partially allows a lateral expansion ofthe inner and outer tarsus of the foot of the user of the ski boot,which tarsus expands to both sides when the foot is moving, inparticular when the lower leg is being moved or tilted forward withrespect to the foot, in the inner 27 and outer tarsus area 28 of thefront foot shell 2, a recess 29 is designed in the stiffening part 3.This recess 29 is achieved by a curved returning of the edge section26—FIGS. 2 and 3—of the stiffening part 3 underneath the two ankle areas12, 13 in direction heel area 10. The section of the front foot shell 2in the region of the recess 29 of the stiffening part is thus formedfrom the plastics material being relatively flexible compared to thestiffening part 3, resulting in an increased flexibility of the frontfoot shell 2 in this region. In order to nevertheless achieve asufficient increase of stability by the stiffening part 3 it isfunctional that the edge section 26 of the stiffening part 3 underneaththe inner 27 and outer tarsus area 28 and thus underneath the recess 29extends diagonally downwards or forward in the direction towards themiddle section of the sole area 21 and the toe area 23 of the front footshell 2.

According to a particular advantageous embodiment, the at least onestiffening part 3 of the front foot shell 2 is formed from a plasticmaterial with a plurality of independent fibers 32 in a randomizedarrangement—FIG. 2—in particular carbon fibers. Advantageously, thisfiber-reinforced, high-tensile plastics has a modulus of elasticity ofup to 12 GPa, preferably a modulus of elasticity of 0.9 GPa to 1.5 GPa,so that the front foot shell 2 in its rear region is correspondinglydimensionally stiffened by the stiffening part 3.

Due to the fact that the numerous fibers 32 independently from eachother are added to the plastic material of the stiffening part 3 in arandomized arrangement, it is according to an advantageous embodimentpossible for the stiffening part 3 to be also produced by means of aninjection molding process, where the fibers 32 are added to a plasticmaterial before the front foot shell 2 is actually produced, inparticular on the basis of injection molding. In order to allow for thenumerous, independent fibers 32 to be added to the plastic materialduring the manufacturing process, in particular the injection molding ofthe stiffening part 3, in a randomized arrangement on the one hand, andeffect for the produced stiffening part 3 to have a highest possiblestability it is advantageous if the fibers 32 have an average length of2 mm to 7 mm.

It is also advantageous if the section 6 not covered by the at least onestiffening part 3 is formed from a plastic material being relativelyflexible compared to the stiffening part 3 and having a modulus ofelasticity of 0.1 GPa to 0.8 GPa, preferably having a modulus ofelasticity of 0.1 GPa to 0.4 GPa. Thus, a relatively flexible formationof the front foot shell 2 is achieved in the section 6 of the front footshell 2 not covered by the stiffening part 2. Due to the usage ofmaterials providing different properties, in particular differentsurface properties, it is furthermore possible to design components ofshell parts, in particular stiffening parts 3, and components, notcovered by stiffening parts 3, of the front foot shell 2 havingdistinctive haptics. As a material for the relatively flexible plasticmaterial in particular thermoplastic polyurethane (TPU) is used, whichcan also be used as a basic material for the production of thefiber-reinforced stiffening part 3.

According to an advantageous embodiment, the at least one stiffeningpart 3 of the front foot shell 2 has a thickness of 2 mm to 3 mm,preferably 2.5 mm. Such a relatively thin stiffening part 3, which isinjection-back-molded with only a relatively thin layer of flexibleplastic material in the further course of the production process, allowsthe production of a front foot shell 2, the shell thickness of which isreduced compared to the front foot shells known from prior art, with theresult that a front foot shell 2 having a relatively lower weight can beproduced at consistent or even increased stability.

The front foot shell 2 in the section covered by the at least onestiffening part 3 preferably has an average thickness of 3 mm to 7 mm,preferably of averagely 4 mm to 5 mm. As already mentioned, the wallthickness of the front foot shell 2 reduced compared to the prior artallows the production of a shell 1 of a ski boot, which has a reducedweight at constantly high stability values. With an alternative,advantageous embodiment, the wall thickness of the front foot shell 2compared to prior art is not reduced, but the stability of the plasticmaterial being relatively flexible compared to the stiffening part 3 ischosen lower than usual, with the result that the shell 1 of the skiboot at constant stability values in the section covered by the at leastone stiffening part 3 has an increased flexibility in the section 6 notcovered by the stiffening part 3.

According to a particularly advantageous embodiment, which is best to beseen in FIGS. 2 and 3, the at least one stiffening part 3 has in itsedge section 26 a connection element 33, with the result that aparticular durable or stable connection between the stiffening part 3and the thereto adjacent, relatively flexible plastic material iscreated. An additional improvement of the connection properties isachieved by embodying one or more apertures 34 between the inner and theexterior surface of the connection element 33, which apertures 34 arefilled with relatively flexible plastic material during the productionprocess of the front foot shell 2.

A still further increasing if the durability or resistance of theconnection between the at least one stiffening part 3 and the theretoadjacent, relatively flexible plastic material of the front foot shell 2is achieved by the embodiment of at least one transverse element 35 inthe edge section of the connection element 33.

From the FIGS. 4 and 5, illustrations of a longitudinal section and across-section of the shell 1 of the ski boot can be taken. In FIG. 4,also a cuff 18 of a ski boot is shown in longitudinal section, which isfurthermore shown in a separate oblique view in FIG. 6. Furtherembodiments of stiffening parts 25, 43 can be taken from FIGS. 4 to 6,to which the basic explanations of the description of the stiffeningpart 3 above are applied analogously.

According to one of the advantageous embodiments shown in FIGS. 4 and 5,a stiffening part 43 is formed in the sole area 21 of the front footshell 2 of the ski boot from the heel area 10 to the toe area 23.Spacers 44 at the interior surface 45 of the stiffening part 43 are madefor the simple and exact positioning of the front foot shell 2.Different from the stiffening part 3, not only the interior surface 45but also the exterior surface 46 of the stiffening part 43 is covered bythe relatively flexible plastic material during this injection moldingprocess. The stiffening part 43, which can be rigidly connected to thestiffening 3 in the heel area 10, can amongst other things be used toinfluence the bending properties of the front foot shell 2 along itslongitudinal axis and to increase the stability and dimensionalstability of the front foot shell 2. By means of the stiffening part 43,in particular the forces appearing in the front foot shell 2 of the skiboot shall be transmitted to a ski via the rear extension of sole 15 anda front extension of sole 16, particularly via a binding, in the mostdirect and targeted way possible.

According to an embodiment not shown it is also advantageous to disposeone or more further stiffening elements in the metatarsus area 22 and/orin the lateral or upper section of the toe area 23 of the front footshell 2 in order to increase the stability of the front foot shell 2.

FIGS. 4 and 6 shoe a further, advantageous embodiment of a shell 1according to the invention of a ski boot, where a stiffening part 25 isintegrated into the cuff 18 of the ski boot, which stiffening partprovides the shell 1 in the lower area of the lower leg 24 with anincreased stability. The stiffening part 25 particularly increases thedimensional stability of the cuff 18 in its rear region and partiallyalso in its rear lateral regions due to the special design of thestiffening part 25, as it is best to be seen in FIG. 6. The section 36of the cuff 18 not covered by the stiffening part 25 is formed from aplastic material being relatively flexible compared to the stiffeningpart 25, with the result that the wear comfort of the ski boot isincreased. Due to this fact, particularly relatively flexible flaps 42can be formed at the cuff 18, which in connection with a not showntensioning mean allow a simple closing free of clearance of the cuffaround the lower leg of a user.

Furthermore, the stiffening part 25 reinforces both sides of the cuff 18in the regions corresponding to the apertures 17 of the front foot shell2, where also apertures 41 are embodied. The front foot shell 2 and thecuff 18 are connected in a flexible way via the connection elements inthe apertures 17 and 41.

As indicated in FIG. 6, the stiffening part 25 is in the edge section 30where the relatively flexible plastic material follows equipped with aconnection element 31, with the result that a stable and durableconnection between the stiffening part 25 and the relatively flexibleplastic material of the section 36 of the cuff 18 not covered by thestiffening part 25 is provided. During the manufacturing of the cuff 18,particularly during an injection molding process, the exterior surfacesof the connection element 31 are covered by the relatively flexibleplastic material. In order to achieve a particularly stable connection,the connection element 31 is furthermore equipped with apertures 40,which are filled with the relatively flexible plastic material duringthe injection molding process.

As FIGS. 4 and 6 show, the stiffening part 25 is at its interior surfaceequipped with a plurality of spacers 37, which are used for simply andexactly positioning stiffening part 25 the on a last. Before themanufacturing of the cuff 18, the stiffening part 25 is positioned on alast in such a way that the end sections 38 or the bearing surfaces 39of the spacers 37 rest against the last and a cavity results between theinterior surface of the stiffening part 25 and the surface of the last.In the following injection molding process, this cavity is filled withthe relatively flexible plastic material and also the section 36 of thecuff 18 not being covered by the stiffening part 25 is formed from therelatively flexible plastic material. Once the injection molding processis completed, the end sections 38 or the bearing surfaces 39 of thespacers 37 are arranged flush with the interior surface of the cuff 18.

Particularly advantageous is also the combination of the stiffeningparts 3, 25, 43 in a shell 1 of a sports shoe 1, in particular a skiboot, shown in FIG. 4. Due to the arrangement of the stiffening parts 3,25, 43, a high stability of the shell 1 is provided in its rear and hearlateral section of the lower area of the lower leg 24, in the area ofAchilles' tendon, heel area 10, ankle area 12, 13 and area of anklejoint 19, 20 and in the sole area 21 to the toe area 23. All remainingregions of the shell 1 are formed from a relatively flexible plasticmaterial, with the result that a sports shoe is created, which isconvenient and comfortable to wear on the one hand and allows a quickand sporty moving or going on the other hand.

For the sake of good order, finally, it should be pointed out that inorder to provide a clearer understanding of the device for convertingenergy, it and its constituent parts are illustrated to a certain extentout of scale and/or on an enlarged scale and/or on a reduced scale.

The embodiments illustrated as examples illustrate possible designvariants of the shell of a sports shoe, and it should be pointed out atthis stage that the invention is not restricted to the variousembodiments specifically illustrated and instead, various combinationsof the individual embodiments with one another are possible, thesepossible variations being within the reach of the person skilled in thisfield based on the technical teaching outlined in the invention.Accordingly, all conceivable variations which can be obtained bycombining individual details of the embodiments illustrated anddescribed are possible and fall within the scope of the invention.

The underlying objective and the solutions proposed by the invention maybe found in the description.

Above all, the individual embodiments of the subject matter illustratedin FIGS. 1 to 3; 4 to 6 may be construed as independent solutionsproposed by the invention in their own right. The objectives andassociated solutions proposed by the invention may be found in thedetailed descriptions of these drawings.

LIST OF REFERENCE NUMERALS

-   1 Shell-   2 Front foot shell-   3 Stiffening part-   4 Interior surface-   5 Spacer-   6 Not covered section-   7 End portion-   8 Bearing surface-   9 Interior surface-   10 Heel area-   11 Area of Achilles' tendon-   12 Inner ankle area-   13 Outer ankle area-   14 Exterior surface-   15 Rear extension of sole-   16 Front extension of sole-   17 Aperture-   18 Cuff-   19 Inner area of ankle joint-   20 Outer area of ankle joint-   21 Sole area-   22 Metatarsus area-   23 Toe area-   24 Lower area of lower leg-   25 Stiffening part-   26 Edge section-   27 Inner tarsus area-   28 Outer tarsus area-   29 Recess-   30 Edge section-   31 Connection element-   32 Fiber-   33 Connection element-   34 Aperture-   35 Transverse element-   36 Not covered section-   37 Spacer-   38 End section-   39 Bearing surface-   40 Aperture-   41 Aperture-   42 Flap-   43 Stiffening part-   44 Spacer-   45 Interior surface-   46 Exterior surface

1. A shell of a sports shoe comprising: one or more three-dimensionalshell parts having a certain stability, at least one of the shell partscomprises a stiffening part having a higher stability than the othershell parts including an interior surface and a plurality of spacersprotruding from the interior surface and the interior surface is atleast partially covered by relatively flexible plastic material, thespacers having outermost end portions extending furthest away from theinterior surface arranged substantially flush with the relativelyflexible plastic material, but the outermost end portions of the spacersnot being covered by the relatively flexible plastic material, such thatthe outermost end portions of the spacers can be seen at the interiorsurface of the shell part.
 2. The shell of a sports shoe according toclaim 1, wherein the stiffening part of a shell part is formed from aplastic material with a plurality of independent carbon fibers, added ina randomized arrangement, which material has a modulus of elasticity ofup to 12 GPa.
 3. The shell of a sports shoe according to claim 2,wherein the carbon fibers have an average fiber length of 2 mm to 7 mm.4. The shell of a sports shoe according to claim 1, wherein thestiffening part is arranged to cover a section of the shell, and anothersection of the shell is formed from a plastic material being relativelyflexible compared to the stiffening part and having a modulus ofelasticity of 0.1 GPa to 0.8 GPa.
 5. The shell of a sports shoeaccording to claim 1, wherein the stiffening part has a thickness of 2mm to 3 mm.
 6. The shell of a sports shoe according to claim 1, whereinthe stiffening part is arranged to cover a section of the shell havingan average thickness of 3 mm to 7 mm.
 7. The shell of a sports shoeaccording to claim 1, wherein the stiffening part includes an edgesection and at least one connection element arranged at the edgesection, the at least one connection element includes exterior surfacessurrounded by relatively flexible plastic material compared to thestiffening part.
 8. The shell of a sports shoe according to claim 7,wherein the connection element in the edge section of the stiffeningpart has apertures between interior and exterior surface in the edgesection, which are filled with the relatively flexible plastic material.9. The shell of a sports shoe according to claim 1, wherein thestiffening part includes an exterior surface, and more than 70% of theexterior surface can be seen from the exterior surface of the shell andis not covered by the relatively flexible plastic material.
 10. Theshell of a sports shoe according to claim 1, wherein the sports shoecomprises a heel area, an ankle area, an ankle joint area, a sole area,a metatarsus area, a toe area, and a lower leg area, the stiffening partcomprises a plurality of stiffening parts and are arranged to at leastpartially cover the heel area, the ankle area, the ankle joint area, thesole area, the metatarsus area, the toe area and/or the lower area ofthe lower leg of the sports shoe.
 11. The shell of a sports shoeaccording to claim 1, wherein the shell comprises a rear and lateralregion, the stiffening part is arranged to stabilize the rear andlateral regions.
 12. The shell of a sports shoe according to claim 11,wherein the stiffening part essentially covers the inner and outer anklearea and that the edge section of the stiffening part underneath the twoankle areas returns in direction of the heel area in a curved way, sothat the inner and outer tarsus areas of the stiffening part remainrecessed or not covered and thus, the sections of the shell part thereare only formed from the plastic material being relatively flexiblecompared to the stiffening part and that the edge sections of thestiffening part underneath the inner and outer tarsus areas extendsdiagonally downwards or forwards in the direction towards the middlesection of the sole area and towards the toe area of the shell part. 13.The shell of a sports shoe according to claim 1, wherein the stiffeningpart at least partially covers the rear side and the rear lateralregions of the lower area of the lower leg, with the result that atleast in the rear region and in the rear lateral regions of the shellpart, a dimensionally stiffened shell formation is provided.
 14. Amethod for producing a shell of a sports shoe, in particular a ski boot,with the shell being formed from one or more shell parts and at leastone shell part being formed from compositing several three-dimensionalcomponents, which are each made of a plastic material or metal having acertain stability or elasticity and two of each of the shell parts areconnected in an articulated or rigid way in order to form the shell ofthe sports shoe, characterized in producing at least one stiffeningpart, which forms a three-dimensional component of a shell part, whichstiffening part has a higher stability than the other components of theshell parts and which stiffening part has one or more spacers protrudingfrom the interior surface of the stiffening part, positioning of the atleast one stiffening part on a last defining at least a part of theinterior of the shell part in such a way that the outermost end portionsof the spacers which are furthest away from the interior surface of thestiffening part rest against the surface of the last and thus, aclearance between the interior surface of the stiffening element and thesurface of the last is created, injection-overmolding of a region orsection of the surface of the last not covered by the at least onestiffening part with a plastic material being relatively flexiblecompared to the stiffening part and injection-back-molding of the atleast one stiffening part with the plastic material being relativelyflexible compared to the stiffening part, with the result that theclearance between the interior surface of the stiffening part and thesurface of the last are filled by the relatively flexible plasticmaterial and with the end portions of the spacers bearing against thesurface of the last not being covered by the relatively flexible plasticmaterial.